1. Field of the Invention
The present invention relates to a drive circuit device of a motor and a motor having the same.
2. Description of Related Art
In a drive circuit device, which is provided in a motor to control operation of the motor, a control circuit (IC) and high heat-generating elements (e.g., a drive transistor, a diode, a coil and an electric current sensing resistor) are both provided in a common circuit board. When heat, which is generated by these circuit elements, is conducted to the heat sensitive control circuit, the heat could cause failure of the control circuit. Thus, a control circuit, which has a high rated temperature, needs to be used, and this disadvantageously results in an increase in the manufacturing costs.
Japanese Unexamined Patent Publication No. 2001-251833 discloses a motor, which addresses such a problem. In this motor, the drive circuit device is received in a circuit protective case, which is provided in a lower part of the motor. The drive circuit device includes a filter circuit, a switching circuit and a control circuit. The filter circuit removes surge or the like from the supplied electric power. The switching circuit changes an electric current path to the motor to change a magnetic field generated in the motor. The control circuit controls timing for switching the electric current path of the switching circuit to control rotation of the motor. The filter circuit includes a field-effect capacitor, a choke coil and a wiring bus bar and is installed in an inner case. The switching circuit includes a plurality of switching elements (the drive transistors), which switch the electric current path. The switching elements are urged against the heat sink member arranged above the switching elements. Furthermore, the control circuit includes a control IC and a Hall element. The control IC controls the timing for switching the electric current path of the switching elements. The Hall element senses a rotational position of the motor in cooperation with the sensor magnet. The switching circuit and the control circuit are arranged in the circuit board.
A partition wall, which divides the circuit protective case into two parts, is integrally formed with the circuit protective case and the inner case. The partition wall divides the circuit board into a part, in which the switching circuit is formed, and another part, in which the control circuit is formed. This partition wall controls transmission of the heat, which is generated from the switching elements, to the control circuit.
However, in the motor disclosed in Japanese Unexamined Patent Publication No. 2001-251833, the partition wall is newly provided in the circuit protective case to limit transmission of the heat, which is generated from the switching elements, to the control circuit. Thus, the structure becomes complicated. Furthermore, the provision of the circuit protective case causes an increase in a size of the drive circuit device and also an increase in a size of the motor.